EP0485866B1 - Switching circuit for operating a discharge lamp - Google Patents

Switching circuit for operating a discharge lamp Download PDF

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Publication number
EP0485866B1
EP0485866B1 EP91118851A EP91118851A EP0485866B1 EP 0485866 B1 EP0485866 B1 EP 0485866B1 EP 91118851 A EP91118851 A EP 91118851A EP 91118851 A EP91118851 A EP 91118851A EP 0485866 B1 EP0485866 B1 EP 0485866B1
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EP
European Patent Office
Prior art keywords
power supply
switched
mode power
capacitor
lamp
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP91118851A
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German (de)
French (fr)
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EP0485866A1 (en
Inventor
Franz Bernitz
Andreas Huber
Frank Hansmann
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Osram GmbH
Original Assignee
Patent Treuhand Gesellschaft fuer Elektrische Gluehlampen mbH
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/24—Circuit arrangements in which the lamp is fed by high frequency ac, or with separate oscillator frequency
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/288—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps without preheating electrodes, e.g. for high-intensity discharge lamps, high-pressure mercury or sodium lamps or low-pressure sodium lamps
    • H05B41/2881—Load circuits; Control thereof
    • H05B41/2882—Load circuits; Control thereof the control resulting from an action on the static converter
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/382—Controlling the intensity of light during the transitional start-up phase
    • H05B41/388—Controlling the intensity of light during the transitional start-up phase for a transition from glow to arc
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S315/00—Electric lamp and discharge devices: systems
    • Y10S315/07—Starting and control circuits for gas discharge lamp using transistors

Definitions

  • the invention relates to a clocked switching power supply according to the preamble of protection claim 1.
  • Switching power supplies of this type are part of electronic ballasts for high-pressure discharge lamps, in particular high-pressure discharge lamps with low power consumption.
  • EP-A-0 256 231 discloses a switching power supply with a control circuit which is suitable for discharge lamps.
  • the capacitor at the output of the switching power supply is used to supply energy to the discharge lamp during the conducting phase of the switching transistor.
  • the capacitance of this capacitor should be chosen so large that the supply current of the discharge lamp is only from a small AC component, which results from the high-frequency switching frequency of the transistor, is superimposed. This prevents the discharge in the lamp from going out during the conducting phase of the switching transistor.
  • the capacitance of the capacitor on the output side must be sufficiently small so that the voltage across this capacitor can be set to the lamp operating voltage quickly enough via the pulse width ratio of the switching regulator.
  • Document FR 2 489 069 discloses a circuit arrangement with a ballast and an igniter for a high-pressure discharge lamp, the lamp being connected via the igniter to a capacitor arranged at the output of the ballast.
  • this circuit arrangement has a low-frequency choke coil, which is arranged between the aforementioned capacitor and the lamp.
  • the lamp current is pressed to a relatively low value when the lamp voltage is sufficiently high, so that a glow discharge occurs only at a small front point of the cathode in order to preheat the cathode and thus ensure a safe transition from the glow. to ensure arc discharge.
  • low-frequency choke coils are relatively voluminous and therefore cannot be used in compact ballasts.
  • the RC element parallel to the output capacitor has a relatively large time constant, so that a small but longer-lasting discharge current flows from the capacitor of the RC element, which in connection with the relatively high, but only briefly tig flowing discharge current of the output capacitor, the ignition with subsequent arc acceptance in the discharge lamp ensured.
  • a time-variable resistor can also be connected between the switching power supply and the high-pressure discharge lamp in series with the lamp.
  • This resistor can consist of a thermistor or a parallel connection of a resistor with a mechanical relay contact.
  • the high resistance value of the resistor prevents a high discharge current from flowing out of the output capacitor for a short time. It is only through the onset of self-heating - in the case of the thermistor - or through the closing of the relay contact in parallel connection that an increased current flow is made possible, so that the start of the lamp is guaranteed to work properly.
  • FIG. 1 shows the basic structure of an electronic ballast for a 35 watt metal halide high-pressure discharge lamp L with a switching power supply according to the invention and an ignition circuit Z.
  • the switching power supply is a secondary clocked throttle step-up converter (boost converter).
  • the control part S is not the subject of the invention and is therefore only shown schematically. An example of this can be found eg in EP-A-0 059 053.
  • As voltage source U Batt. serves a 12 volt car battery.
  • An input capacitor C E with a capacitance of 5000 ⁇ F is connected in parallel with the voltage source.
  • a power MOSFET is used as the switching transistor T Q , the gate voltage of which is keyed at a frequency of 20-75 kHz by means of the control circuit.
  • the choke step-up converter also includes a choke L S with an inductance of 0.5 mH, a diode D and an output capacitor C A with a capacitance of 3.3 ⁇ F.
  • An RC element is connected in parallel with the output capacitor C A , whose ohmic resistance R has a value of 33 ⁇ and whose capacitor C R has a capacitance of 22 ⁇ F.
  • the 35-watt high-pressure discharge lamp L is connected in series with the ignition circuit Z in parallel with the output capacitor C A and in parallel with the RC element. Examples of the ignition circuit Z are described in the article "Ignition of metal halide lamps" by H.-J.Fähnrich and H.Leyendecker, predominantly- und Kino-Technik 1972, No. 8, p.279.
  • the load circuit with the discharge lamp L is completely separated from the circuit which is formed by the battery, the inductor L S and the transistor T Q because of the diode D.
  • the energy supply of the lamp L is mainly ensured by the output capacitor C A during the conducting phase of the transistor T Q.
  • the battery and the choke L S take over the voltage supply for the discharge lamp L.
  • the capacitors C A and C R are also charged to the output voltage of the switching power supply.
  • the control circuit regulates the output voltage of the Switching power supply via the pulse duty factor of the switching transistor T Q to the lamp lamp voltage of approx. 100 V.
  • the RC element only serves as an ignition aid.
  • the output capacitor C A supplies a high discharge current of approximately 50 A for a short period of approximately 3 ⁇ s, which generates a “hot spot” on the electrodes of the lamp, but is not sufficient for the lamp after the ignition pulse to be transferred to the arc discharge. Only the slowly decaying, relatively small discharge current of the capacitor C R , the initial value of which is approximately 5 A, together with the discharge current of the output capacitor C A enables the lamp to be ignited safely.
  • FIG. 2 shows a modified embodiment of the basic structure of an electronic ballast for a 35-watt metal halide high-pressure discharge lamp.
  • the exemplary embodiment largely corresponds to the example shown in FIG. 1.
  • a thermistor H is connected in series with the high-pressure discharge lamp L.
  • the invention is not limited to the exemplary embodiment described here, but can equally well be applied to other switching power supplies, such as can be applied to a flyback converter (isolated ornonisolated) or a buck converter (buck converter).
  • a flyback converter isolated ornonisolated
  • buck converter buck converter

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  • Circuit Arrangements For Discharge Lamps (AREA)
  • Dc-Dc Converters (AREA)

Description

Die Erfindung betrifft ein getaktetes Schaltnetzteil gemäß dem Oberbegriff des Schutzanspruchs 1.The invention relates to a clocked switching power supply according to the preamble of protection claim 1.

Derartige Schaltnetzteile sind Bestandteil von elektronischen Vorschaltgeräten für Hochdruckentladungslampen, insbesondere Hochdruckentladungslampen kleiner Leistungsaufnahme.Switching power supplies of this type are part of electronic ballasts for high-pressure discharge lamps, in particular high-pressure discharge lamps with low power consumption.

Schaltnetzteile, die auch in elektronischen Vorschaltgeräten von Entladungslampen Verwendung finden, sind aus der gängigen Fachliteratur bekannt. In der EP-A-0 256 231 wird ein Schaltnetzteil mit einer Steuerschaltung offenbart, das für Entladungslampen geeignet ist.Switched-mode power supplies, which are also used in electronic ballasts for discharge lamps, are known from the current specialist literature. EP-A-0 256 231 discloses a switching power supply with a control circuit which is suitable for discharge lamps.

Untersuchungen haben ergeben, daß bei Verwendung nur eines Kondensators am Ausgang des Schaltnetzteils in Vorschaltgeräten für Hochdruckentladungslampen kleiner Leistungsaufnahme Probleme bei der Zündung dieser Lampen auftreten. Der Kondensator am Ausgang des Schaltnetzteils dient zur Energieversorgung der Entladungslampe während der Leitphase des Schalttransistors. Die Kapazität dieses Kondensators ist dabei so groß zu wählen, daß der Versorgungsstrom der Entladungslampe nur von einem kleinen Wechselstromanteil, der von der hochfrequenten Schaltfrequenz des Transistors herrührt, überlagert wird. Damit wird ein Erlöschen der Entladung in der Lampe während der Leitphase des Schalttransistors unterbunden. Andererseits muß die Kapazität des ausgangsseitigen Kondensators hinreichend klein sein, damit die Spannung an diesem Kondensator schnell genug über das Pulsweitenverhältnis des Schaltreglers auf die Lampenbrennspannung eingestellt werden kann. Beide Anforderungen können zwar vom ausgangsseitigen Kondensator erfüllt werden, allerdings treten beim Zündvorgang, bedingt durch die schlagartige Entladung desr relativ kleinen Kapazität dieses Ausgangskondensators, erhebliche Probleme auf. Die Dauer des Entladestromes des Ausgangskondensators reicht nicht aus, um den Übergang der Hochdruckentladungslampe in die Bogenentladung sicherzustellen.Studies have shown that when using only one capacitor at the output of the switching power supply in ballasts for high-pressure discharge lamps with low power consumption, problems occur when these lamps are ignited. The capacitor at the output of the switching power supply is used to supply energy to the discharge lamp during the conducting phase of the switching transistor. The capacitance of this capacitor should be chosen so large that the supply current of the discharge lamp is only from a small AC component, which results from the high-frequency switching frequency of the transistor, is superimposed. This prevents the discharge in the lamp from going out during the conducting phase of the switching transistor. On the other hand, the capacitance of the capacitor on the output side must be sufficiently small so that the voltage across this capacitor can be set to the lamp operating voltage quickly enough via the pulse width ratio of the switching regulator. Although both requirements can be met by the output-side capacitor, considerable problems arise during the ignition process due to the sudden discharge of the relatively small capacitance of this output capacitor. The duration of the discharge current of the output capacitor is not sufficient to ensure the transition of the high-pressure discharge lamp into the arc discharge.

In der Druckschrift FR 2 489 069 wird eine Schaltungsanordnung mit einem Vorschaltgerät und einem Zündgerät für eine Hochdruck-Entladungslampe offenbart, wobei die Lampe über das Zündgerät an einen am Ausgang des Vorschaltgerätes angeordneten Kondensator angeschlossen ist. Zur Verbesserung der Zündfähigkeit der Lampe weist diese Schaltungsanordnung eine Niederfrequenzdrosselspule auf, die zwischen dem vorgenannten Kondensator und der Lampe angeordnet ist. Durch diese Maßnahme wird, während der Zündphase, der Lampenstrom bei ausreichend hoher Lampen spannung auf einen relativ niedrigen Wert gedrückt, so daß nur an einer kleinen vorderen Stelle der Kathode eine Glimmentladung auftritt, um die Kathode vorzuheizen und so einen sicheren Übergang von der Glimm- zur Bogenentladung zu gewährleisten. Nachteilig ist allerdings, daß Niederfrequenzdrosselspulen relativ voluminös sind und daher nicht in kompakten Vorschaltgeräten verwendet werden können.Document FR 2 489 069 discloses a circuit arrangement with a ballast and an igniter for a high-pressure discharge lamp, the lamp being connected via the igniter to a capacitor arranged at the output of the ballast. To improve the ignitability of the lamp, this circuit arrangement has a low-frequency choke coil, which is arranged between the aforementioned capacitor and the lamp. As a result of this measure, the lamp current is pressed to a relatively low value when the lamp voltage is sufficiently high, so that a glow discharge occurs only at a small front point of the cathode in order to preheat the cathode and thus ensure a safe transition from the glow. to ensure arc discharge. However, it is disadvantageous that low-frequency choke coils are relatively voluminous and therefore cannot be used in compact ballasts.

Es ist die Aufgabe der Erfindung, ein Schaltnetzteil als Bestandteil eines elektronischen Vorschaltgerätes für Hochdruck-Entladungslampen bereitzustellen, das einen störungsfreien Betrieb und eine gute Zündwilligkeit der Lampe gewährleistet.It is the object of the invention to provide a switching power supply as a component of an electronic ballast for high-pressure discharge lamps, which ensures trouble-free operation and good ignitability of the lamp.

Diese Aufgabe wird erfindungsgemäß durch die kennzeichnenden Merkmale des Anspruchs 1 oder 2 gelöst. Besonders vorteilhafte Ausführungen der Erfindung sind in den Unteransprüchen dargelegt.This object is achieved by the characterizing features of claim 1 or 2. Particularly advantageous embodiments of the invention are set out in the subclaims.

Das RC-Glied parallel zum Ausgangskondensator besitzt eine relativ große Zeitkonstante, so daß ein kleiner, aber länger andauernder Entladestrom aus dem Kondensator des RC-Gliedes fließt, der in Verbindung mit dem relativ hohen, aber nur kurzzei tig fließenden Entladestrom des Ausgangskondensators die Zündung mit anschließender Bogenübernahme bei der Entladungslampe sichergestellt. Anstelle des RC-Gliedes parallel zum Ausgangskondensator kann auch zwischen das Schaltnetzteil und die Hochdruckentladungslampe in Reihe zur Lampe ein zeitlich veränderbarer Widerstand geschaltet werden. Dieser Widerstand kann aus einem Heißleiter oder aus einer Parallelschaltung eines Widerstandes mit einem mechanischen Relaiskontakt bestehen. Zum Zeitpunkt der Zündung verhindert der Widerstand durch seinen hohen Widerstandswert, daß aus dem Ausgangskondensator ein hoher Entladestrom kurzzeitig abfließen kann. Erst durch die einsetzende Eigenerwärmung - im Falle des Heißleiters - oder durch die Schließung des Relaiskontaktes bei der Parallelschaltung wird ein erhöhter Stromfluß ermöglicht, so daß der Anlauf der Lampe einwandfrei gewährleistet ist.The RC element parallel to the output capacitor has a relatively large time constant, so that a small but longer-lasting discharge current flows from the capacitor of the RC element, which in connection with the relatively high, but only briefly tig flowing discharge current of the output capacitor, the ignition with subsequent arc acceptance in the discharge lamp ensured. Instead of the RC element parallel to the output capacitor, a time-variable resistor can also be connected between the switching power supply and the high-pressure discharge lamp in series with the lamp. This resistor can consist of a thermistor or a parallel connection of a resistor with a mechanical relay contact. At the time of ignition, the high resistance value of the resistor prevents a high discharge current from flowing out of the output capacitor for a short time. It is only through the onset of self-heating - in the case of the thermistor - or through the closing of the relay contact in parallel connection that an increased current flow is made possible, so that the start of the lamp is guaranteed to work properly.

Die Erfindung wird im folgenden anhand der nachfolgenden Ausführungsbeispiele näher erläutert.

Figur 1
zeigt ein elektronisches Vorschaltgerät mit einem RC-Glied.
Figur 2
zeigt ein elektronisches Vorschaltgerät mit einem Heißleiter.
The invention is explained in more detail below with reference to the following exemplary embodiments.
Figure 1
shows an electronic ballast with an RC element.
Figure 2
shows an electronic ballast with a thermistor.

Die Figur 1 zeigt den prinzipiellen Aufbau eines elektronischen Vorschaltgerätes für eine 35-Watt Halogen-Metalldampf-Hochdruckentladungslampe L mit einem erfindungsgemäßen Schaltnetzteil und einer Zündschaltung Z. Derartige Lampen und Vorschaltgeräte werden in Kfz-Scheinwerfern eingesetzt. Bei dem Schaltnetzteil handelt es sich um einen sekundär getakteten Drossel-Aufwärtswandler (Boost-converter). Das Steuerteil S ist nicht Gegenstand der Erfindung und ist daher nur schematisch dargestellt. Ein Beispiel hierfür findet sich z.B. in der EP-A-0 059 053. Als Spannungsquelle UBatt. dient eine 12 Volt-Kfz-Batterie. Parallel zur Spannungsquelle ist ein Eingangskondensator CE mit einer Kapazität von 5000 µF geschaltet. Als Schalttransistor TQ wird ein Power-MOSFET verwendet, dessen Gate-Spannung mittels der Steuerschaltung mit einer Frequenz von 20 - 75 kHz getastet wird. Zu dem Drossel-Aufwärtswandler gehören ferner eine Drossel LS mit einer Induktivität von 0,5 mH, eine Diode D und ein Ausgangskondensator CA mit einer Kapazität von 3,3 µF. Parallel zum Ausgangskondensator CA ist ein RC-Glied geschaltet, dessen ohmscher Widerstand R einen Wert von 33Ω besitzt und dessen Kondensator CR eine Kapazität von 22 µF aufweist. Die 35-Watt Hochdruckentladungslampe L ist mit der Zündschaltung Z in Reihe parallel zum Ausgangskondensator CA und parallel zum RC-Glied angeschlossen. Beispiele für die Zündschaltung Z sind in dem Artikel "Zündung von Halogen-Metalldampflampen" von H.-J.Fähnrich und H.Leyendecker, Fernseh- und Kino-Technik 1972, Nr.8, S.279 beschrieben.1 shows the basic structure of an electronic ballast for a 35 watt metal halide high-pressure discharge lamp L with a switching power supply according to the invention and an ignition circuit Z. Such lamps and ballasts are used in motor vehicle headlights. The switching power supply is a secondary clocked throttle step-up converter (boost converter). The control part S is not the subject of the invention and is therefore only shown schematically. An example of this can be found eg in EP-A-0 059 053. As voltage source U Batt. serves a 12 volt car battery. An input capacitor C E with a capacitance of 5000 µF is connected in parallel with the voltage source. A power MOSFET is used as the switching transistor T Q , the gate voltage of which is keyed at a frequency of 20-75 kHz by means of the control circuit. The choke step-up converter also includes a choke L S with an inductance of 0.5 mH, a diode D and an output capacitor C A with a capacitance of 3.3 μF. An RC element is connected in parallel with the output capacitor C A , whose ohmic resistance R has a value of 33Ω and whose capacitor C R has a capacitance of 22 μF. The 35-watt high-pressure discharge lamp L is connected in series with the ignition circuit Z in parallel with the output capacitor C A and in parallel with the RC element. Examples of the ignition circuit Z are described in the article "Ignition of metal halide lamps" by H.-J.Fähnrich and H.Leyendecker, Fernseh- und Kino-Technik 1972, No. 8, p.279.

Während der Leitphase des Transistors TQ ist der Laststromkreis mit der Entladungslampe L wegen der Diode D von dem Stromkreis, der durch die Batterie, die Drossel LS und dem Transistor TQ gebildet wird, vollkommen getrennt. Die Energieversorgung der Lampe L wird während der Leitphase des Transistors TQ hauptsächlich vom Ausgangskondensator CA sichergestellt. Während der Sperrphase des Transistors TQ übernehmen die Batterie und die Drossel LS die Spannungsversorgung der Entladungslampe L. Dabei werden auch die Kondensatoren CA und CR auf die Ausgangsspannung des Schaltnetzteils aufgeladen. Die Steuerschaltung regelt die Ausgangsspannung des Schaltnetzteils über das Tastverhältnis des Schalttransistors TQ auf die Lampenbrennspannung von ca. 100 V. Das RC-Glied dient lediglich als Zündhilfe. Während der Zündung der Hochdruckentladungslampe liefert der Ausgangskondensator CA für eine kurze Zeitdauer von ca. 3 µs einen hohen Entladestrom von ungefähr 50A, der auf den Elektroden der Lampe einen "Hot-spot" erzeugt, aber nicht ausreicht, um die Lampe nach dem Zündimpuls in die Bogenentladung überzuführen. Erst der langsamer abklingende, relativ kleine Entladestrom des Kondensators CR, dessen Anfangswert ungefähr 5A beträgt, ermöglicht zusammen mit dem Entladestrom des Ausgangskondensators CA die sichere Zündung der Lampe.During the conducting phase of the transistor T Q , the load circuit with the discharge lamp L is completely separated from the circuit which is formed by the battery, the inductor L S and the transistor T Q because of the diode D. The energy supply of the lamp L is mainly ensured by the output capacitor C A during the conducting phase of the transistor T Q. During the blocking phase of the transistor T Q , the battery and the choke L S take over the voltage supply for the discharge lamp L. The capacitors C A and C R are also charged to the output voltage of the switching power supply. The control circuit regulates the output voltage of the Switching power supply via the pulse duty factor of the switching transistor T Q to the lamp lamp voltage of approx. 100 V. The RC element only serves as an ignition aid. During the ignition of the high-pressure discharge lamp, the output capacitor C A supplies a high discharge current of approximately 50 A for a short period of approximately 3 μs, which generates a “hot spot” on the electrodes of the lamp, but is not sufficient for the lamp after the ignition pulse to be transferred to the arc discharge. Only the slowly decaying, relatively small discharge current of the capacitor C R , the initial value of which is approximately 5 A, together with the discharge current of the output capacitor C A enables the lamp to be ignited safely.

Figur 2 zeigt ein abgewandeltes Ausführungsbeispiel des prinzipiellen Aufbaus eines elektronischen Vorschaltgerätes für eine 35-Watt Halogen-Metalldampf-Hochdruckentladungslampe. Das Ausführungsbeispiel stimmt weitgehend mit dem in Figur 1 dargestellten Beispiel überein. Anstelle des RC-Gliedes parallel zum Ausgangskondensator ist jedoch hier ein Heißleiter H in Reihe zur Hochdruckentladungslampe L geschaltet.Figure 2 shows a modified embodiment of the basic structure of an electronic ballast for a 35-watt metal halide high-pressure discharge lamp. The exemplary embodiment largely corresponds to the example shown in FIG. 1. Instead of the RC element parallel to the output capacitor, however, a thermistor H is connected in series with the high-pressure discharge lamp L.

Die Erfindung ist nicht auf das hier beschriebene Ausführungsbeispiel beschränkt, sondern kann ebensogut auf andere Schaltnetzteile, wie z.B. auf einen Drossel-Inverswandler (Flyback-converter, isolated ornonisolated) oder einen Tiefsetzsteller (Buck-converter) angewendet werden.The invention is not limited to the exemplary embodiment described here, but can equally well be applied to other switching power supplies, such as can be applied to a flyback converter (isolated ornonisolated) or a buck converter (buck converter).

Claims (7)

  1. Switched-mode power supply having pulse-width modulation for converting one DC voltage into another DC voltage for operating a high-pressure discharge lamp (L) by means of an ignition circuit (Z), the switched-mode power supply containing one or more active (TQ) and passive (D) semiconductor switches, one or more inductors (LS) and, in each case parallel to the input and output of the switched-mode power supply, a capacitor (CE, CA), characterized in that a RC element (R, CR) having a relatively large time constant is connected in parallel with the capacitor (CA) at the output of the switched-mode power supply, so that a longer-lasting discharge current flows from the capacitor (CR) of the RC element (R, CR) during the ignition phase of the lamp.
  2. Switched-mode power supply having pulse-width modulation for converting one DC voltage into another DC voltage for operating a high-pressure discharge lamp (L) by means of an ignition circuit (Z), the switched-mode power supply containing one or more active (TQ) and passive (D) semiconductor switches, one or more inductors (LS) and, in each case parallel to the input and output of the switched-mode power supply, a capacitor (CE, CA), characterized in that a temporally variable resistor (H) is connected, in series with the lamp, between the output of the switched-mode power supply and the high-pressure discharge lamp (L), which resistor has a high resistance at the time when the lamp (L) is ignited.
  3. Switched-mode power supply according to Claim 1, characterized in that the capacitor (CA) at the output of the switched-mode power supply has a capacitance of between 0.01 µF and 25 µF.
  4. Switched-mode power supply according to Claim 1, characterized in that the capacitance of the capacitor (CR) in the RC element (R, CR) has a capacitance of between 0.5 µF and 25 µF.
  5. Switched-mode power supply according to Claim 1, characterized in that the ohmic resistor (R) of the RC element (R, CR) has an electrical resistance of between 10 Ω and 100 Ω.
  6. Switched-mode power supply according to Claim 2, characterized in that the temporally variable resistor is a thermistor (H) having a cold resistance of between 10 and 100 Ω.
  7. Switched-mode power supply according to Claim 2, characterized in that the temporally variable resistor is a parallel circuit of a resistor with a mechanical relay contact.
EP91118851A 1990-11-15 1991-11-05 Switching circuit for operating a discharge lamp Expired - Lifetime EP0485866B1 (en)

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Application Number Priority Date Filing Date Title
DE9015674U DE9015674U1 (en) 1990-11-15 1990-11-15
DE9015674U 1990-11-15

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EP0485866A1 EP0485866A1 (en) 1992-05-20
EP0485866B1 true EP0485866B1 (en) 1996-01-31

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US (1) US5343125A (en)
EP (1) EP0485866B1 (en)
JP (1) JPH0499697U (en)
KR (1) KR0120598Y1 (en)
DE (2) DE9015674U1 (en)

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DE9015674U1 (en) 1992-03-12
KR0120598Y1 (en) 1998-10-01
JPH0499697U (en) 1992-08-28
EP0485866A1 (en) 1992-05-20
DE59107339D1 (en) 1996-03-14
US5343125A (en) 1994-08-30
KR920010795U (en) 1992-06-17

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